In recent years, display and input devices having touch panels, which are input devices, installed on the front surfaces of display devices such as liquid crystal displays have been put into practical use and are being used in operation panels of portable devices, such as mobile telephones, and home appliances. Display and input devices using touch panels enable the user to intuitively operate the device by pressing the display on the screen.
Touch panels that have been put into practical use so far have only been able to detect the position the user has pressed (in the present specification, this will sometimes be called “touch position”) and have not been able to detect the force with which the user has pressed the touch panel (that is, the height (force) of the pressing; in the present specification, this will sometimes be called “touch pressure”). In display and input devices using touch panels, the touch panel is installed on the front surface of the display device, so it is required that the transparency of the touch panel be high in order to raise the visibility of the display of the display device.
As an input device or something similar that is capable of detecting the force of the pressing and is transparent, for example, Japanese Patent Unexamined Publication No. 2006-163619 discloses a touch panel portion that is used as a member of electronic paper and comprises a piezoelectric, a first electrode disposed on one side of the piezoelectric, and a second electrode disposed on the other side of the piezoelectric.
Further, Japanese Patent Unexamined Publication No. 2004-534974 discloses a touchscreen system comprising: a first sensor system coupled to a touchscreen, said first sensor system determining a set of position coordinates for each touch of said touchscreen; and a second sensor system coupled to said touchscreen, said second sensor system confirming each touch of said touchscreen by a first type of object, and invalidating each touch of said touchscreen by a second type of object, wherein said second sensor system is incapable of determining said set of position coordinates. And as the first sensor system, specifically force sensors placed outside the viewing area of an LCD are disclosed.
Further, Japanese Patent Unexamined Publication No. 2004-125571 discloses a transparent piezoelectric sensor in which a transparent pressure-sensitive layer that is piezoelectric and a pair of transparent conductive film layers that are placed opposing each other via the transparent pressure-sensitive layer are formed on a pair of transparent substrates that oppose each other.